Pre-emergence herbicides influence the efficacy of fungicides in controlling cotton seedling damping-off in the field

Abstract

Two field experiments were conducted in Safford and Tucson, Arizona to investigate the impact of three pre-emergence herbicides (pendimethalin, prometryn and trifluralin) on the efficacy of commonly used fungicides (metalaxyl, triadimenol and thiram) against Rhizoctonia solani a soil borne fungus causing cotton seedling damping-off Pendimethalin, prometryn and trifluralin were applied to the field soil at the recommended field concentrations of 0.9, 1.3 and 0.7 kg active ingredient (a.i.) ha-1, respectively. In both field trials, seed treatment with fungicides caused a significant (p<0.05) decrease in fungal pathogenicity based on the number of emerged cotton seedlings, relative to the control (not treated with the fungicide). In Tucson trail, only one of the test herbicides (pendimethalin) interfered with the ability of fungicides to reduce the pathogenicity of Rhizoctonia solani on cotton seedlings 15, 25 and 50 days after sowing. In Safford trial, the effectiveness of fungicides on fungal pathogenicity was reduced in the presence of pendimethalin and prometryn, 15, 25 and 50 days after sowing. Trifluralin showed no significant effect on the activity of fungicides in both field trials. © 2007 Academic Journals Inc.